The present invention relates to an extensible film or sheet and a process for producing the same. More particularly, the invention relates to an extensible film or sheet having excellent flexibility and extensibility, good hand feeling and fine hand and drape, and suited for use as a diaper gather, diaper back sheet, film used for making foundry molding, pallet stretch film and the like.
Extrusion molded films made from very low-density ethylene copolymers having a density of less than 0.910 g/cm.sup.3 tend to suffer from blocking between the films when they are formed according to an ordinary film forming method, due to small crystal portion and a large amount of low-molecular-weight components of the film. The conventional methods of forming said films also had the problem of causing surface roughening of the film because of high viscosity under a low shear rate.
As a solution to this problem, it has been proposed to add an anti-blocking agent such as synthetic silica, a lubricant such as metallic soap or a placticizer in large quantities. These measures, however, were unable to produce a satisfactory effect, and rather there could take place bleeding of the additive to give rise to the problems in drape, hand feeling and sanitation.
Use of additives also had the problem of increased production cost.
Thus, it has been difficult with very-low-density ethylene copolymers to produce the practically usable films because of the defects such as mentioned above, in spite of their excellent extensibility and flexibility in comparison with ordinary polyethylenes.
In view of the above, the present inventors have made further researches on the very-low-density ethylene copolymer films having excellent flexibility and extensibility and, as a result, found that by modifying a material comprising a very-low-density ethylene copolymer or comprising a specific linear polyethylene and a very-low-density ethylene copolymer with a radical forming agent and forming this modified material into a film, it is possible to obtain an extensible film which is excellent in various properties. The present invention was achieved on the basis of this finding.